Late night Facebook and Twitter sessions make everyone depressed, and researchers at Ohio State University Medical Center think they know why: It has less to do with vanity Google searches or looking up old friends on Facebook, and more to do with sitting in front of a glowing screen in the dark. Their research revealed changes in behavior and the brain after those late night sessions in front of unnatural light symptomatic of depression.

The study, published in Molecular Psychiatry, concluded that while there's still research to be done, the preliminary response in hamsters to dim, unnatural light at night reflected previously observed changes in human behavior, and closely mimicked symptoms of depression (in the hamsters, it was drinking nothing but sugary water and being generally lethargic.) For the rest of us, the solution is simple: keep the lights on as long as the computers are on, or keep your computing to daylight hours.